Multiple telephone switch-board



(No Model.) 4 2 Shets- Sheet 1. P. A. PIGKERNELL.

MULTIPLE TELEPHONE SWITCH BOARD.

Patented Nov. 17, 1 891.

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(No Model.) 2 Sheets-Sheet 2 P. A. PIGKERNELL. MULTIPLE TELEPHONE SWITCH BOARD.

No. 463,544. Patented Nov. 17, 1891;

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FRANK A. PIOKERNELL, OF NEXVARK, NEW JERSEY.

MULTIPLE TELEPHONE SWITCH-BOARD.

SPECIFICATION forming part of Letters Patent N 0. 463,544, dated November 17, 1891.

Application filed August 17, 1891,

To all whom it may concern:

Be it known that I, FRANK A. PIOKERNELL, residing at Newark, in the county of Essex and State of New Jersey, have invented certain Improvements in Multiple Telephone Switch-Boards, of which the following is a specification.

Multiple switch-boards for telephone-exchange central stations are of two general classes, namely: first, those of which the form shown in Letters Patent of the United States No. 305,021, granted September 9, 1884, to Charles E. Scribner, is a type, in which the main circuits pass to the several switch-board sections in successive loops and then to a suitable calling device. On each switchboard section of this class the loop terminals of the several circuits are each provided with a plug-socket or other attachment, including separable spring-contacts, whereby on the insertion of a plug-connector the circuit may be broken, cutting off its normal route through the call-instrument and connecting the outgoing end or ends with a new path or paths through a conductor or conductors (according to whether the circuit is earth-completed or metallic) leading from the said plug to any other such circuit similarly arranged for the purpose of interconnection; second, those of the type illustrated and described in Letters Patent of the United States No. 252,576, granted to Leroy B. Firman, January 17,1882, in which the main circuits pass to the several switch-board sections by independent norn1ally-discontinuous branches, which are represented on the said sections by terminals in the form of plug-sockets or similar connections of a simple character, in which separable spring-contacts are not required, whereby any two such circuits may be united through any suitable conductor, such as a flexible conducting-cord provided with a plugconnector at both ends.

My present invention relates to multiple switch-boards of the latter class. boards of this class have heretofore not largely been used, for the reason that when the several main circuits connected therewith have been worked in connection with call-annunciators (they being simply branched to the switch-sections) no simple plan has presented itself whereby the insertion of a con- S witch Serial No. 402,902. (No model.)

' necting-plug for the purpose of making condevice, which, if unbroken, would ordinarily constitute a shunt or derived ,circuit to the through talking-circuit, introducing several features decidedly objectionable in practice and materially interfering with the efficient operation of the circuits; such for example as dropping the annunciator of a line wanted, at the answering-switch section of. said line in sending acall to the sub-station connected therewith; a partial short-,circuiting of the voice-currents through the call device or normal circuit-route of both of two connected lines; and, finally, the reception of a disconnecting-signal not only by the disconnectingannunciator at the point where any two lines were connected, but also by the original callindicating devices of both lines concerned, and the consequent misunderstanding which such a multiplication of signals would involve. These difficulties have usually been avoided, where switch-boards of this classhave been employed, by adopting the expedient of the Firman patent, to which reference has been made, which is to dispense altogether with a call device included in the working circuits, thus enabling such circuits to remain normally open and to send the calls over a dis tinct circuit.

The object of my invention is to permit the use of closed circuits and call-annunciators, as usual, avoiding the necessity of extra callcircuits, and at the same time to overcome the difficulties which have been recited.

To this end it consists in employing for the regular signal-receivin g annunciators or callindicators electro-maguets of relatively high resistance and self-induction, and for the disconnecting or clearing-out annunciators magnets of relatively low resistance. In thus providing a normal circuit which may remain closed without interfering with the proper operation of the circuits, and in combining these with a multiple switch-board in which the several circuits connected with said switch-board branch to the several switchboard sections.

In the drawings which form a part of this specification, Figure 1 is a diagram indicating a three-section multiple switch-board, and three metallic circuits branching to each, each of the said circuits being ultimately terminated or having its call-annuneiator located at a dilferent section. Fig- 2 is a diagram of two circuits complete, extending each from an exchange-station to a central station, and united at one section of a branchingmultiple switch-board; and Fig. 3 is a detail diagram of a ringing-key and its connections adapted for use and forming part of my invention.

In Fig. 1, S S S are respectively operating-sections of a telephone central office multiple switch-board M. L, U, and L are metaliic main telephone circuits, each extending from an exchange or subscribers station to the said switch-board M, and provided each with an electro-magnetic call device at some one of the operative switch-board sections, so that any two of them may be united by suitable link-conductors at any section. A, at switch-board section S,is the call-annunciator of'circuit L. A at section S is the annunciator of circuit L and A at section S is the annuncia-tor of line L Thus the incoming calls of L are received at switchboard section S, those of L at S and those of L at S and it will further appear that whenever a connection is made between anytwo lines such connection is always at the section at which the call-annunciator of one of the said lines is located,because acall from any circuit for another can only be initiated at the section where the annunciator of the calling-circuit is placed. The circuits shown being metallic, lead through the switch-board to their several annunciators each by conductor 1*, and then back therefrom by conductor Z The conductor Z of each circuit has at each switchboard section a terminal or connection attachment 8, (in this case a plug-socket) while the other conductor Z of each circuit has placed in close proximity to its mate a second similar connection or socket .9 These connections are united to the circuit-conductors which they represent by short branch wires. Thus circuitL branches to its sockets s and 3 011 the three sections shown S, S and S respectively, by the several pairs of branches 5 6, 3 4:, and 1 2. Circuit L branches to its terminals by ll 12, 9 10, and 7 8, and circuit L branches to its terminals by 17 18, 15 10, and 1314. These pairs of branch circuits being normally discontinuous,-do not interfere with the regular operation in calling of the call-annunciatorA. At each switch-board section any required number of interconnection links or appliances N are placed, (but one being shown in the drawings) which conveniently may be formed of double conductors 19 20, inclosed in a flexible cord provided atits ends with lu -connectors P I each having two members p 1.1 which are preferably mounted upon a common insulating-handle R. The conductor 20 unites the member 17,

while the conductor 19 unites members 192.

nector formed with a single member having two condnoting-surfaces insulated from each other and in circuit respectively with condoctors 19 and 20 would be employed. Bridged across between the link-conductors 19 and 20 of each link appliance N, by means of supplementary conductors 30 and 31,is a disconnecting or olearing-out annunciator cl. It will be seen that the two conductors of L and L constitute when connected, as shown I at section S, a through metallic circuit be tween the exchange-stations X and Y, (indi cated by circles and dotted linesin Fig. 1 and more fully in Fig. 2,) that the disconnectingannunciator (Z is bridged across the said metallic circuit and is adapted to be operated by and from either sub-station, and that the normal extensioircircuits 3 33, through the higlrresistance annunciator A, constitutes virtually also a second and third bridge or derived circuit from the points a: and 1 of the main circuits L and L which are in parallelism with and shunt the extension of each of said main circuits through the other; but I find that by properly constructing and proportioning the electro-magnets of said annunciators their presence and the permanent connection of the parallel circuits in which they areincluded is rendered perfectlyinnocnous.

The disconnecting-annunciator (Z may be constructed as usual with an iron core and tubular case, and I have found a resistance of two hundred ohms to answer well in practice. It is connected in the usual way and is not found to interfere with efficient operation.

The regular main-circuit annunciators A, A and A are wound to a very high resistance. I have experimentally found a resistance as high as sixteen thousand chars to serve the purpose perfectly, although an annunciator having a resistance as low as three thousand five hundred ohms gives fairly satisfactory results. They are designed to develop a maximum amount of self-induction, and when connected as shown, the two highresistance and self-induction annunciators A are shunted by the disconnecting-annunciator, the resistance of which is so low as to prevent the former altogether-from operating nected with telephonic apparatus T to a 0011- connected in any desired way.

'tral station Z, where both are connected'with a multiple switch-board M, which, as hereinbefore described, has at each of its sections S S &c., branch terminals of all the circuits entering the station, to which terminals the similar terminals of any other circuit may be Each circuit is at all times closed at the central station through a regular high-resistance and selfinduction annunciator A. At section S the two lines are shown as being connected for conversation by means of double connectors 19 and 20 and their terminal plugs, which unite the plug-sockets, s and s of the two lines, and which are themselves united through the bridge-conductors 30 and 31 and the low-resistance annunciator d. The selfinduction of the annunciator cl is sufficient to prevent it from at all impairing the conversation transmitted between the sub-stations, and since that of the call-annunciator A and A is much higher than that of d it is clear that these also will not shunt the voicecurrent, all three, in fact,acting as retardation or choking coils, so far as the conversation-currents are concerned; and I have also found that when in addition to raising the resistance of the regular calling-annunciators in the manner described, the call-generator at the central station is shunted by'a resistance equivalent to that of the clearing-out annunciator, as indicated in Fig. 3, during the act of sending an outgoing signal over any circuits to the sub-station called for, the said call can be sent without operating the call-annunciator of .said circuit, which may be located at some other section of .the switch-board, and which, were it to respond, might be regarded by the operator at such other section as a call-signal. In the figure the circuit L, connecting the telephone appliances T at station X with the call-annunciator A at the central station Z, is shown. Two of the terminal plates .9 s of said circuit are shown as being united by conductors l9 and 20 to the two members k and k of the ringing-key K, which when depressed brings the said members respectively into contact with conducting-plates'n and 0, which are the terminals of a callgenerator V, and at the same time also brings the terminals of said generator into contact with the ends e and f of a resistance 1', equivalent to that of the clearing-out annunciator.

Any of thewell-known busy-test systems may be employed in connection with this multiple switch-hoard arrangement, and although I have described and prefer a switch -board particularly adapted and arranged for metallic circuits, it is evident that my invention is equally applicable to switch-boards in which the main circuits to be manipulated utilize the earth as a return-conductor.

I claim 1. A multiple telephone switch-board comprising main circuits having normally-discontinuous branches leading to connection terminals'at its several sections, a relatively-high resistance electro-magnetic call device permanently included in each main circuit at some one of the said sections, means at each switchboard section for electrically uniting any two circuits by connecting their respective branch terminals, and a disconnecting-ann unciator of relatively low resistance bridged between the direct and return conductors of any two circuits when so united in a branch circuit shunting the high-resistance call devices of the said circuits. 1

2. The combination, substantially as hereinbefore described, of two metallic circuits,

' each permanently closed at a central station through a call-annunciator helix of relatively high resistance and se1f-induction, a double conductor link connection uniting the direct and return conductors of one of the said circuits with those of the other, and a clearing out or disconnecting annunciator located in a bridge-conductor between the two conductors of said link connection and serving to shunt the said high-resistance call-annunciators.

3. In atelephone-exchange system, two metallic circuits, each extending from a different sub-station to the same central station and there having their respective direct and return conductors united to constitute a single compound metallic circuit from one of the said sub-stations to the other, in combination with two bridge-conductors, each uniting the direct and return conductors of said compound metallic circuit through an ann [111* ciator-helix of relatively high resistance, and "a third bridge uniting the said direct and return conductors through anannunciator-helix of relatively low resistance and shunting the said high-resistance helices, substantially as described.

4. The combination, substantially as hereinbefore described, of aclosed main telephonecircuit extending from a telephone call-bell 'at a sub-station to a call-annunciator of relatively high resistance at a central station and connected at said central station by normallydiscontinuous branch conductors with connection terminals at each of a series of switch.- sections, a link-connection conductor at each switch-section adapted to unite the connection terminals of said main circuit with those of another similar circuit, and a relatively low resistance-dis'connectin'g annunciator included in the circuit thereof, a magnetocall generator forsending outgoing-calls currents to the said sub-station for the operation of said call-bell associated with said link connection, a shunt-resistance substantially equivalent to that of said disconnecting-annunciator, and a ringing-key or equivalent device adapted to connect said generator with the said main circuit and to simultaneously close a shunt-circuit, including the said shuntresistance between the poles of said generator.-

5. In a metallic circuit multiple switchboard comprising several operative sections, a series of metallic circuits, each branching to paired connection, terminal sockets located at every section and each looping through a call-annunciator helix of relatively-high resistance and self-induction at some one of the said sections, a double conductor link connection at each section terminating at both ends thereof by plug-connectors having two conducting surfaces or members and adapted to be inserted, respectively, in the said terminal sockets of any two lines and thereupon to unite the said two lines without breaking their normal circuits through their respecttive. call-annunciators, and a disconnectingor clearing-out annunciator havingahelix of relatively-low resistance eonnectedby a crossconductor from one of the conductors of said link connection to the other and constituting, when the said link connection is connected with any circuit, a shunt-circuitround the high-resistance call-annunciator of such circuit, substantially as and for the purposes specified.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 8th day of August, A. D. 1891.

FRANK A. PICKERNELL;

Witnesses:

S. W. DUNBAR, C. J. PICKERNELL. 

